Theses and Dissertations from UMD
Permanent URI for this communityhttp://hdl.handle.net/1903/2
New submissions to the thesis/dissertation collections are added automatically as they are received from the Graduate School. Currently, the Graduate School deposits all theses and dissertations from a given semester after the official graduation date. This means that there may be up to a 4 month delay in the appearance of a give thesis/dissertation in DRUM
More information is available at Theses and Dissertations at University of Maryland Libraries.
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Item PHOTO-GUIDED SHAPE TRANSFORMATION OF COMPOSITE HYDROGEL SHEETS(2018) Guo, Hongyu; Nie, Zhihong; Chemistry; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Shape-changing hydrogel material has numerous potential applications in biomimetics, soft robotics, biomedicine, etc. Light as a clean energy source can be remotely delivered to material with high spatial and temporal resolution, which brings new controllability to shape-transformation of hydrogel material. However, the current strategy of using light to control deformation of hydrogel is limited. This dissertation aims to develop new approaches to program shape-transformation of hydrogel material by using light. First, I developed a simple and efficient approach to re-program shape-transformation of composite hydrogel sheet with homogeneously distributed silver nanoparticle. By modulating light irradiation pattern, the same hydrogel sheet transformed to multiple distinct geometries, which were verified by finite element method. Secondly, I developed a simple and reliable approach to pattern various types of photo-thermal converting nanoparticles in hydrogel sheet. The approach enables nanoparticle patterning in both lateral and thickness-direction of hydrogel, which cannot be readily achieved by other approaches such as microcontact printing and photo-lithography. Thirdly, I explored shape transformation of composite hydrogel sheet with spatially patterned plasmonic gold nanoparticles fabricated by using the approach mentioned above. The same patterned composite hydrogel sheet can be designed to exhibit distinct shape transformation modes, highly depending on light irradiation direction, which has not been reported before. Fourthly, I studied shape transformation of composite hydrogel sheet spatially patterned with erasable and rewritable iron oxide nanoparticles. The same hydrogel sheet was re-programmed to exhibit various distinct shape transformations by changing nanoparticle pattern. This provides a new method to reprogram shape transitions of hydrogel material by using external light source. In addition, a hydrogel tube was also readily patterned with iron oxide nanoparticles and its deformation was studied as well. Lastly, I developed a simple and general approach to fabricate multifunctional composite hydrogel tube. The hydrogel tube was formed via self-rolling of 2D hydrogel sheet after releasing stress introduced during photo-polymerization. The introduced magnetic nanorod brought multi-functionality to the hydrogel tube. The self-rolled tube was used to load, transport and release cargo manipulated by capillary force, magnet and light, respectively. This dissertation provides a new, simple and efficient toolset to program and re-program shape transformation of composite hydrogel material by using external light. It is believed that the toolset and concept developed in this dissertation can be applied to other light-responsive hydrogel material.Item Authentication of Fingerprint Scanners(2012) Ivanov, Vladimir Iankov; Baras, John S; Electrical Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)To counter certain security threats in biometric authentication systems, particularly in portable devices (e.g., phones and laptops), we have developed a technology for automated authentication of fingerprint scanners of exactly the same type, manufacturer, and model. The technology uses unique, persistent, and unalterable characteristics of the fingerprint scanners to detect attacks on the scanners, such as detecting an image containing the fingerprint pattern of the legitimate user and acquired with the authentic fingerprint scanner replaced by another image that still contains the fingerprint pattern of the legitimate user but has been acquired with another, unauthentic fingerprint scanner. The technology uses the conventional authentication steps of enrolment and verification, each of which can be implemented in a portable device, a desktop, or a remote server. The technology is extremely accurate, computationally efficient, robust in a wide range of conditions, does not require any hardware modifications, and can be added (as a software add-on) to systems already manufactured and placed into service. We have also implemented the technology in a demonstration prototype for both area and swipe scanners.Item Connecting Community: Capturing and Patterning Orphan Space in Langley Park(2011) Pagan Aello, Jessica Alexandra; Kim, Julie J; Architecture; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Alleys and parking lots provide but a few examples of orphan or "in-between" space--of residual land spawned by 1960s urbanism. These unclaimed spaces have latent qualities, often only visible to a community's inhabitants. These spaces, like all spaces, morph to reflect cultural values and needs. Their difference lies in their residual nature. They allow the disenfranchised to learn, sell, and gather flexibly. They lie in between "valued" and "value-less" space. Modern urban theory fails to address these spaces, instead overlooking the micro-patterning of space. By incorporating these spaces into a careful study of pattern at the scale of the city, community, building, and individual, one can connect a once fragmented community. Langley Park provides the case study for addressing these issues of urbanism, orphan space, and connectivity--it provides an example of capturing, patterning, and connecting orphan space at all scales.Item Pattern Process: An Exploration of Non-Architectonic Seams(2008) Healey, Jonathan; Wortham-Galvin, BD; Architecture; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)The re-purposing of a two-hundred year-old river-side factory site involves a complex set of extant, historical, and hypothetical considerations, and requires a system of strategies and tactics beyond the conventional scope of historic preservation or formal architectural analysis. The discovery of cultural patterns, both physical and social, becomes the alibi for an even broader exploration of design methodology. By reviving the etymology of "pattern" as the co-joining of autonomous pieces to create form and volume, a conceptual study of pattern and seams seeks to develop an implicit methodology that first reveals non-architectonic structural relationships, then engages these structures as determinants in the re-design of the existing built environment. The proposed framework is tested against an architectural agenda that seams historic patterns of human activity and site conditions with speculative patterns of event, process, and technology for the creation of a place expressing contemporary ideology among the continuity of living history.